We are investigating the capacity of the retina to carry out the biosynthesis of its mannose-containing glycoproteins, with special emphasis being placed on the biosynthesis of the saccharide moieties of the glycoprotein, rhodopsin. We are studying the biosynthesis and properties of polyisoprene-mannose-containing lipids by the retina, and are investigating their role in the biosynthesis of glycoproteins, as well as the participation of vitamin A and its analogues in these processes. These studies are being carried out primarily with preparations from the retina of the embryonic chick and with rat and bovine retinas. We are also investigating the chemistry of the carbohydrate components of bovine rhodopsin.